1. Field of the Invention
The present invention relates generally to soft pack structures such as stuffsacks, backpacks or rucksacks adapted to contain articles for transport, and more particularly to a soft pack structure having enhanced integrity against water infiltration, the structure including a substantially conventional outer pack structure of pliable water resistant material having an opening defined therein and means to close and cover such pliable opening, and an inner bag structure also of water resistant, pliable material adapted to fit within the outer pack structure and cooperate with the closure means of the upper outer pack structure to facilitate attachment of the inner bag structure to the outer pack structure and provide for concurrent closure of both.
2. Description of the Prior Art
Soft pack structures such as backpacks, stuffsacks, rucksacks etc. are of course well known. The better quality of such packs are formed of wear resistant, woven material coated on one side therewith with a substantially water impervious material, typically a nylon or polyester cloth coated on one side with a urethane material to resist water penetration. In many instances, such packs are utilized to carry clothing, food stuffs, equipment etc. critical to the very survival of the user. Heretofore such pack structures have provided only limited resistance to moisture penetration under adverse conditions, i.e., rain, wet snow, water spray etc. While the materials from which the pack structures are constructed are in fact highly water resistant as a result of coatings such as the urethane coatings, the water resistant integrity of such structures is severely compromised by the many perforations in typical pack structures, i.e., for seams to form the pack structure itself, and to attach panels, bottoms, shoulder straps, pockets, holding loops, and various other sewn constructions and features. While the synthetic materials and water resistant coatings thereon are highly resistant to water penetration, such materials are not self healing around perforations. Thus water readily infiltrates through the many needle and other holes formed in the pack structure as an unavoidable result of conventional production of such pack structures.
To combat the serious threat of wetting of the contents of the pack structure, it has heretofore been the practice to wrap the separate, or entire, contents of the sack in individual waterproof enclosures, such as polymer film bags commonly employed as "garbage" bags. Such efforts, while inconvenient, are often effective. However, in the instance of film enclosures, during the course of an extended expedition, it is not unusual for the polymer film bags to become ripped and perforated.
It has also been customary to line certain pack bags with a second layer of material to decrease water penetration through the coated surfaces. However, this type of construction does not diminish total seams (and subsequent reduced needle hole water penetration) since the lining is simply a mirror image of the outer material layers and has identical seam placement and number as the outer material layer.